I. Field of the Invention
The present invention relates to data communication. More particularly, the present invention relates to a novel and improved method and apparatus for processing a physical channel with partial transport format information.
II. Description of the Related Art
A modern day communications system is required to support a variety of applications. One such communications system is a code division multiple access (CDMA) system that supports voice and data communication between users over a terrestrial link. The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” and U.S. Pat. No. 5,103,459, entitled “SYSTEM AND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM,” both assigned to the assignee of the present invention and incorporated herein by reference.
A CDMA system is typically designed to conform to one or more standards. One such first generation standard is the “TIA/EIA/IS-95 Remote Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,” hereinafter referred to as the IS-95 standard and incorporated herein by reference. IS-95 compliant CDMA systems are able to transmit voice data and packet data. A newer generation standard is offered by a consortium named “3RD Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214, which are readily available to the public. The 3GPP standard is hereinafter referred to as the W-CDMA standard and incorporated herein by reference.
The W-CDMA standard defines a channel structure capable of supporting a number of users and designed for efficient transmission of packet data. In accordance with the W-CDMA standard, a user is typically assigned a “dedicated” channel on the downlink (i.e., from the base station to the user) and the uplink (i.e., from the user to the base station) for the duration of the call. The dedicated channel can be used for voice communication or transmission of small amounts of packet data, and thus has a (relatively) low bit rate. When the base station has a large amount of data to transmit, a “shared” channel may be assigned and used for the data transmission. The shared channel is allocated and de-allocated to users as needed.
The shared channel has a structure that supports a variety of uses and a bit rate that can be varied between a range of values (e.g., from 15 kbps up to 1.92 Mbps). The shared channel bit rate can also be dynamically changed from radio frame to radio frame, with each radio frame being a unit of transmission covering 15 time slots and each time slot corresponding to 0.667 msec.
In accordance with the W-CDMA standard, certain information necessary to properly recover the data transmitted on the shared channel is provided on the dedicated channel assigned to the user. For example, in certain instances, the bit rate of the radio frame and the channelization code (akin to the Walsh code in the IS-95 CDMA system) used to channelize the shared channel a re provided on the dedicated channel at approximately the same time as the data transmission on the shared channel. Consequently, the receiver unit is not able to process and recover the data on the shared channel in real-time.
Thus, techniques that can be used to efficiently process a physical channel, such as the shared channel in the W-CDMA system, when some characteristics of the physical channel are not known are highly desirable.